Distance modulus: mod0

When measurements are available in the distance catalogue, mod0 is computed as the weighted average of those measurements. Otherwise, it is determined either using the Tully-Fisher or Faber-Jackson relation for respectively spiral or elliptical galaxies.

The Tully-Fisher relation uses the corrected total magnitude btc and the maximum velocity of rotation vmaxg.
mod0 = btc + 6.5 log(vmaxg) + 6.3

The Faber-Jackson relation uses the corrected total magnitude btc and the central velocity dispersion vdis.
mod0 = btc + 6.2 vdis + 5.9

Another parameter, modz (redshift distance modulus), estimates the luminosity-distance using the redshift.